2936511-35.php

<?php

  /**
   * {@inheritdoc}
   */
  public function __construct($definition) {
    // Only new instances should provide the required revision metadata keys.
    // The cached instances should return only what already has been stored
    // under the property $revision_metadata_keys.
    $this->requiredRevisionMetadataKeys += [
      'revision_default' => 'revision_default',
    ];

    // Move stuff so blah blah blah
    foreach ($this->requiredRevisionMetadataKeys as $key) {
      if (isset($definition['revision_metadata_keys'][$key])) {
        $this->requiredRevisionMetadataKeys[$key] = $definition['revision_metadata_keys'][$key];
        unset($definition['revision_metadata_keys'][$key]);
      }
    }

    parent::__construct($definition);

    $this->handlers += [
      'storage' => 'Drupal\Core\Entity\Sql\SqlContentEntityStorage',
      'view_builder' => 'Drupal\Core\Entity\EntityViewBuilder',
    ];

    // Add the required revision metadata fields here instead in the getter
    // method, so that they are serialized as part of the object even if the
    // getter method doesn't get called, which allows us to further extend the
    // list and let only new instances of the class to contain the new list
    // while the cached instances contain the previous version of the list.
    $this->revision_metadata_keys += $this->requiredRevisionMetadataKeys;
  }